diff --git a/checkpolicy/policy_scan.l b/checkpolicy/policy_scan.l
index 4067268b..129a8a2a 100644
--- a/checkpolicy/policy_scan.l
+++ b/checkpolicy/policy_scan.l
@@ -59,12 +59,17 @@ alnum   [a-zA-Z0-9]
 hexval	[0-9A-Fa-f]
 
 %%
-\n.*				{ strncpy(linebuf[lno], yytext+1, 255);
-                                  linebuf[lno][254] = 0;
-                                  lno = 1 - lno; 
-                                  policydb_lineno++;
-				  source_lineno++;
-                                  yyless(1); }
+\n.*				{
+				  strncpy(linebuf[lno], yytext+1, 255);
+				  linebuf[lno][254] = 0;
+				  lno = 1 - lno;
+				  policydb_lineno++;
+				  if (source_lineno == ULONG_MAX)
+				      yywarn("source line number overflow");
+				  else
+				      source_lineno++;
+				  yyless(1);
+				}
 CLONE |
 clone				{ return(CLONE); }
 COMMON |
@@ -270,7 +275,13 @@ GLBLUB				{ return(GLBLUB); }
 {hexval}{0,4}":"{hexval}{0,4}":"({hexval}|[:.])*  { return(IPV6_ADDR); }
 {digit}+(\.({alnum}|[_.])*)?    { return(VERSION_IDENTIFIER); }
 #line[ ]1[ ]\"[^\n]*\"		{ set_source_file(yytext+9); }
-#line[ ]{digit}+	        { source_lineno = atoi(yytext+6)-1; }
+#line[ ]{digit}+	        {
+				  errno = 0;
+				  source_lineno = strtoul(yytext+6, NULL, 10) - 1;
+				  if (errno) {
+				    yywarn("source line number too big");
+				  }
+				}
 #[^\n]*                         { /* delete comments */ }
 [ \t\f]+			{ /* delete whitespace */ }
 "==" 				{ return(EQUALS); }